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Old 04-10-2014, 03:28 PM   #1
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Default Wort rest?

Been hearing a bunch of pro's who do rest at 145 and then 15 min at say 155-160. I mash in a cooler so while I can do steps, it's not that easy. I was wondering if some of the benefit of the alpha rest could be had by raising the wort to the higher temp and resting for 15 before beginning the boil?


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Old 04-10-2014, 03:48 PM   #2
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I've read Firestone Walker does this and I've tried it on a few beers recently. The point of the 145F rest is to create a very fermentable wort. The rest at 155-156F is to convert some less fermentable sugars that will help with the body. Letting the wort sit (not the grain) at 155F before the boil won't do anything. You need to have the grain sitting in the wort at that temp to try and convert some longer strain sugars, which are the less fermentable sugars.

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Old 04-10-2014, 04:05 PM   #3
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I have done MANY experiments brewing the same beer as a step mash and a single infusion. There was basically no difference.

Actually, since the enzymes are in the wort, you could do a rest with just the wort. Stopping that action is why some people do a mashout.

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Old 04-10-2014, 04:05 PM   #4
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As dobe12 said, once you drain it off the grain it doesn't matter.
If you want to experiment, what might be easier is mash at 145 for 30-45min and drain, then fill with your sparge water to elevate the grain bed temp to the 155-160 range and let sit for 15-30min (kinda like a 2nd mash to get the nonfermentables). Not apples to apples, but easier than a decoction.
How that affects the water chemistry (pH, etc) you'd have to experiment to find out.

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Old 04-10-2014, 08:02 PM   #5
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Professional brewers do a lot of things to squeeze every bit out of their grains that don't make much of a difference at our level. But when you're talking about tons of grains and hundreds of gallons of wort every bit helps to save money. Main thing is to find a process that works best for you.

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Old 04-10-2014, 11:41 PM   #6
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Long chain sugars are basically starch. They're polysaccharides. It can be considered carbohydrates. Wrapped in the starch are monosaccharrides that can be converted to disaccharides, called maltose. Glucose, a monosaccharide, makes up about 10% of starch. After a-amylase liquifies the starch, turning it into carbohydrate soup, it begins chopping up the long chain. A reducing and non-reducing end are formed everywhere the chain is cut. Then, beta chops off two molecules of glucose from only the non-reducing end of the chain, mixing with one water molecule, resulting in maltose. When b-enzyme cuts off three molecules of glucose and blends with one water molecule, maltriose is formed, an trisaccharide. There's something called amylopectin thrown in the mix, too. Disaccharides should make up 55% of the starch. The left overs should be reduced to maltriose and small limit dextrins. In a nutshell, long chain sugar, remains long chain sugar until mashing. Then, a-amylase cuts the chain up. When a and b enzymes can not reduce the sugar/carbo chain any farther, a-limit and b-limit dextrins are formed. The limit dextrins are not fermentable. Long chain sugar remain as such in crystal and cara malt, as enzymes cannot reduce the sugars. A 145 F rest is done, because starch hasn't gelatinized. Beta, slowly produces maltose, the low temp preserves enzymes. If you look at a step mash process for German style ale, wheat, lager and pils. There is usually, a 140-145 F rest. Then another beta rest above gelatinizing temp. Starch gelatinizes at 149 F. Both rests take advantage of a-amylase chopping up the chain, producing many non-reducing ends for b-amylase to work on. Then, a short rest is done at 155-158 F and at 162 F, until conversion. When testing for conversion, unconverted gelatinized starch will cause iodine to be deep red to mahogany. Carried over gelatinized starch reduces the quality of the finished product. During conditioning phase it can open the door for gram negative bacteria. None of that matters if the product goes from boiler to belly in four or five weeks. A decoction method brewer is able to vary the conversion temps in each decoction as well as in the mashtun. Why boil water for infusions, when mash can be boiled? There is much to brewing beer and so little time to drink it all.

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Old 04-11-2014, 10:57 AM   #7
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um... yeah, what he said.

I got my Masters in mechanical engineering 15 years ago but I felt like a freshman in chemistry class reading that. I knew it was more complicated than simply breaking down starches to sugars and dissolving them but wow... Bravo Vlad, you obviously truly enjoy the science of brewing.
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Old 04-11-2014, 02:56 PM   #8
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There's theory and then there's reality...try back to back batches, one single infusion and the other step mashed. Maintain all other variables exactly the same. Then do a blind triangle tasting. I think you'll be surprised.

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Old 04-11-2014, 03:06 PM   #9
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Wow, Vlad, that was really interesting reading!

I'm no good with chemistry EXCEPT as applies to any sort of cooking - and beer is, after all, cooking - so I really enjoyed what you took the time to type out. Thanks.

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